CODEWITHSUNDEEP
pythonkeyboard-events
rennat
rennat

Reputation: 2559

Python cross-platform listening for keypresses?

I need to listen for certain keypresses in a python terminal program without pausing execution with raw_input. I've seen people use a few windows specific ways of listening for keystrokes and I've seen people use large modules like tkinter and pygame which I want to avoid.

Is there a lightweight module out there that does this cross platform (at least ubuntu, windows, mac)? or is there a way to use just the event system from tkinter, pygame, etc...?

If not, how should I approach tackling this? My first thought is to redirect stdin to another process and keep checking to see if it contains one of my event keys.

edit

Thank you @unutbu for taking the time to mark this question that is 3 years old and successfully answered as a duplicate of another question whose answers do not apply to this question because I specifically asked about a non-blocking solution.

Upvotes: 21

Views: 22119

Answers (4)

Guinther Kovalski
Guinther Kovalski

Reputation: 1909

you can use python module plataform, to get the current OS and then make a solution for each platform:

import platform
platform.platform()
'Linux-3.3.0-8.fc16.x86_64-x86_64-with-fedora-16-Verne'

Upvotes: 0

CMCDragonkai
CMCDragonkai

Reputation: 6372

Here's how you can do it on Windows:

"""

    Display series of numbers in infinite loop
    Listen to key "s" to stop
    Only works on Windows because listening to keys
    is platform dependent

"""

# msvcrt is a windows specific native module
import msvcrt
import time

# asks whether a key has been acquired
def kbfunc():
    #this is boolean for whether the keyboard has bene hit
    x = msvcrt.kbhit()
    if x:
        #getch acquires the character encoded in binary ASCII
        ret = msvcrt.getch()
    else:
        ret = False
    return ret

#begin the counter
number = 1

#infinite loop
while True:

    #acquire the keyboard hit if exists
    x = kbfunc() 

    #if we got a keyboard hit
    if x != False and x.decode() == 's':
        #we got the key!
        #because x is a binary, we need to decode to string
        #use the decode() which is part of the binary object
        #by default, decodes via utf8
        #concatenation auto adds a space in between
        print ("STOPPING, KEY:", x.decode())
        #break loop
        break
    else:
        #prints the number
        print (number)
        #increment, there's no ++ in python
        number += 1
        #wait half a second
        time.sleep(0.5)

Upvotes: -1

beer_monk
beer_monk

Reputation: 956

Short answer: no Keypresses are system-dependent. They are interrupt-driven. They one of the basic things built into most modern OSes. They have different philosophies that can't be unified in a generic way without losing functionality.

you might try- termios = unix, posix-style file-descriptor driven

curses = portal terminal-style handling (which is a specific console-based paradigm not generic)

Python wraps certain classes of input that might come from the keyboard: e.g., sys.stdin for console inupt.

But trying to get universal keyboard input is a very general problem that's inherently platform-dependent.

Upvotes: 6

scoffey
scoffey

Reputation: 4688

I don't know of any cross-platform lightweight module that listens for keypresses. But here's a suggestion in case you want to implement something simple:

Check out this question on getting a single keypress at a time in the Python FAQ. You could experiment a bit with blocking reads from sys.stdin and threading. But this may only work on Unix. On Windows, you can use msvcrt.kbhit.

Combining the keypress recipe from the Python FAQ and the msvcrt module, the resulting kbhit function would go like this:

try:
    from msvcrt import kbhit
except ImportError:
    import termios, fcntl, sys, os
    def kbhit():
        fd = sys.stdin.fileno()
        oldterm = termios.tcgetattr(fd)
        newattr = termios.tcgetattr(fd)
        newattr[3] = newattr[3] & ~termios.ICANON & ~termios.ECHO
        termios.tcsetattr(fd, termios.TCSANOW, newattr)
        oldflags = fcntl.fcntl(fd, fcntl.F_GETFL)
        fcntl.fcntl(fd, fcntl.F_SETFL, oldflags | os.O_NONBLOCK)
        try:
            while True:
                try:
                    c = sys.stdin.read(1)
                    return True
                except IOError:
                    return False
        finally:
            termios.tcsetattr(fd, termios.TCSAFLUSH, oldterm)
            fcntl.fcntl(fd, fcntl.F_SETFL, oldflags)

Upvotes: 8

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